The CPU manufacturers all around the world, such as Intel, Cyrix, AMD, etc., make CPUs having special specifications which are set by the manufacturers. Because the CPUs do not have a standard specification therebetween, the methods of generating the CPU working frequencies are different. For example, the method of generating the working frequency of Intel 200 is to multiply 66.667 MHz with 3. The working frequency of Cyrix 200 is obtained by multiplying 75 MHz with 2. The working voltages of all the CPUs made by the same manufacturer are not the same. For example, the working voltage of Intel P54C is 3.3 volts, and P55X is 2.8 volts. The working voltage of Cryix 6X86 is 3.5 volts, while 6X86L is 2.8 volts and 6X86MX is 2.9 volts. The working voltage of AMD K5 is 3.3 volts, while K6 is 2.9 volts or 3.2 volts. The working voltage of K6 which will be available is 2 volts. Because the mother board manufacturers do not know that the users will buy what kind of CPU before the users tell it to them, thus, the available mother boards should have the function of regulatively matching the CPU which is chosen by the user. In the well-known methods, the matching of working frequency is done by changing a CPU multiple frequency coefficient signal and a frequency selection signal of the frequency generator by means of jumpers or switches. In the same way, the working voltage to be provided to the CPU is changed. However, the users are not familiar with the matching methods. Although a user manual for guidance may be provided, the user cannot easily set the jumper or switch. It is difficult and inconvenient for the user to do so. If the setting of the jumper or switch is wrong, the CPU is broken down or the optimum working state of the CPU cannot be set and obtained.
In view of the above drawbacks, several mother board manufacturers proposed some methods to overcome such a problem. For example, Taiwanese Patent Publication No. 297872 discloses a method and device of switching a working frequency of a computer mother board. Taiwanese Patent Publication No. 304239 discloses a method and device of automatically setting a power voltage of a CPU on a mother board. In Taiwanese Patent Publication No. 297872, by means of settings similar to those of mother board BIOS, the CPU multiple frequency coefficient and external working frequency are set by the user directly on the monitor screen. For example, the working frequency of Intel 200 series CPUs is 200 MHz which is obtained by multiplying a base frequency 66.667 MHz with a multiple frequency coefficient 3. The users of Taiwanese Patent Publication No. 297872 set the base frequency and multiple frequency coefficient on the monitor screen, then a computer system can automatically generate the working frequency needed by the CPU through the settings. However, most of the users are not familiar with the computer hardware structure. When the user buys the computer, he generally instructs the model, such as Pentium PRO 200, to be bought. The numeral 200 represents the working frequency of the CPU. Therefore, the users only know this number and do not know the base frequency and the multiple frequency coefficient. The settings will bother the user. The user probably incorrectly takes the base frequency to be the working frequency. When it happens, the system boots at low speed, and when the CPU receives the incorrect settings, the computer probably cannot normally run or the CPU breaks down. Furthermore, the settings of the working frequencies of various CPUs are different, the working voltages are different too. The first Taiwanese patent provides a method of automatically setting the working frequency, but the method of using the different CPU working frequencies is not provided. The goal of plugging and immediately playing the CPUs can not be achieved.
In the second Taiwanese patent, at the location of the jumper on the mother board, a switch is connected in parallel. The voltage levels of the working voltage pin VCC2-DET defined by the CPU respectively represent the using range of working voltage. The pin controls the switch-on or switch-off state of each switch in order to automatically set the working voltage needed by the CPU. However, the switching and settings are made to change between 3.3 volts and 2.8 volts, and cannot meet the requirements of all kinds and models of CPUs. In the second Taiwanese patent, the settings are made in view of working voltage only and the working frequency of CPU is not changed. Therefore, the goal of plugging and immediately playing cannot be achieved.